A drilling machine and a method of the before-mentioned kind are known from EP 1 103 350 A2.
One monitors in that case the power-on condition of an electric motor for driving a tool and an electromagnet that is intended to be attached to a ferromagnetic tool. The current of the electromagnet is reduced in a holding state, in which only the electromagnet is active while the electric motor is inactive, the full holding force being required only during drilling in operating condition.
Such core hole drilling machines, which are attached to a ferromagnetic part being normally the work piece, are exposed to the most diverse operating conditions. Frequently, work is to be performed overhead, or else on girders far above ground. To avoid accidents, extreme labor safety is therefore of great importance.
It has been found in operation that operator errors happen again and again in that the electromagnet sometimes is switched off when the electric motor is still running so that the holding force then no longer suffices to hold the relatively heavy drilling machine and the latter has to be held by one hand alone which leads to an increased risk of accident.
A further core hole drilling machine of a similar kind is known from EP 1 621 286 A2.
That machine comprises a mount on which an electromagnet is provided for attachment to a ferromagnetic metal part on which a drilling unit is supported in displaceable fashion, wherein the drilling unit comprises a housing that accommodates an electric motor intended to drive a tool, and wherein a controller is provided that comprises at least one switch for switching on and off an electric motor and the electromagnet.
The operating elements are arranged in this case on the side of the mount and/or of the housing of the drilling unit. In particular when working overhead or under similarly restricted conditions, the operator's view of the different functions is very limited.